The present invention relates to a bending method of accurately detecting an elongation value of particularly step bending when a plate-shaped workpiece is bent and a apparatus for specifying one-sided elongation value in a bending apparatus.
Conventionally, in a bending apparatus such as a press brake, when a plate-shaped workpiece is bent by cooperation of a punch and a die, an elongation value of step bending is calculated based on many pieces of information including mold data such as a die V width V, a die shoulder are DR, a die groove angle DA, a punch end are PR and a punch angle PA, workpiece data such as bending conditions such as a plate thickness t and a friction coefficient xcexc, material constants such as a Young""s modulus E, a Poisson""s ratio, an F value and an n value of a workpiece, and mechanical data such as a stroke of a ram.
A workpiece is developed, blanked and bent based on the calculated elongation value.
Incidentally, in the conventional bending method and its apparatus, since an elongation value of V bending is calculated by the above elongation value calculating method, there arises a problem that this value does not coincide with an actual elongation value of step bending.
Namely, the most V bending is working for bending totally three points: one point of a punch and two points of a die, but the step bending is working which is not normal V bending and in which V (a width of a V groove of a V-shaped mold)/T (plate thickness) is small and also bending is carried out in a state close to coining. For this reason, the elongation values of the V bending and the step bending are inevitably different from each other even if their other bending conditions (plate thickness, bending angle and the like) have the same values. Therefore, since conventionally the elongation value obtained by the V bending is sued so that the step bending is carried out, an error occurs.
In addition, in order to calculate an elongation value, there arises a problem that many pieces of information such as mold data, workpiece data and mechanical information are necessary.
Therefore, since the calculated elongation value does not coincide with an actual working state as mentioned above, trial bending is carried out in the bending and a finished dimension is actually measured so that an elongation value of the bending is obtained. Therefore, there arises a problem that the step bending requires more time for setup of the bending than the normal V bending.
The present invention is devised in order to solve the above problems, and its object is to provide a bending method of being capable of operating an elongation value of step bending accurately from only two pieces of information including a plate thickness and a bending angle and of carrying out bending, and an apparatus for specifying a one-sided elongation value in the bending apparatus.
In order to achieve the above object, a bending method of the present invention based on a first aspect includes the steps of: before step-bending a workpiece by means of cooperation of a punch and a die, previously carrying out various step bending and making simulation of step bending and calculating an approximation formula based on a correlation between a ratio of a one-sided elongation value to a plate thickens and a step bending angle based on a relationship among the plate thickness, the bending angle and the one-sided elongation value of a workpiece so as to store the approximation formula as a database; at the time of actual bending, capturing two data including a specified plate thickness and a step bending angle into the database so as to calculate a one-sided elongation value based on the approximation formula in the database; and carrying out bending based on the one-sided elongation value.
In the bending method based on the first aspect, the various step bending to be carried out previously is carried out by using a step bending mold to be used at the time of actual bending, carried out later.
In addition, the various step bending to be carried out previously may be carried out by simulation using a step bending mold to be used at the time of actual bending, carried out later.
Therefore, the approximation formula of the correlation between the ratio of the one-sided elongation value to the plate thickness and the step bending angle is previously calculated so as to be stored as a database, and the more accurate one-sided elongation value is obtained easily by less parameters including only two data including the plate thickness and the step bending angle based on the approximation formula. The bending is carried out efficiently and accurately based on the one-sided elongation value without previously carrying out trial step bending.
An apparatus for specifying a one-sided elongation value in a bending apparatus of the present invention based on a second aspect includes: a computing unit for previously carrying out various step bending or making simulation of step bending so as to calculate an approximation formula based on a correlation between a ratio of a one-sided elongation value to a plate thickness and a step bending angle based on a relationship among the plate thickness, the bending angle and the one-sided elongation value of a workpiece; a database file for storing the approximation formula calculated by the computing unit as a database; and a one-sided elongation value computing unit for specifying and capturing a plate thickness and a step bending angle at the time of actual bending into the approximation formula in the database file so as to calculate a one-sided elongation value.
In the apparatus for specifying a one-sided elongation value in a bending apparatus based on the second aspect, the various step bending previously carried out is carried out by using a step bending mold to be used at the time of actual bending, carried out later.
In addition, the various step bending previously carried out may be carried out by simulation using a step bending mold to be used at the time of actual bending, carried out later.
Therefore, the function of the second aspect is similar to the function of the first aspect. The approximation formula of the correlation between the ratio of the one-sided elongation value to the plate thickness and the step bending angle is calculated so as to be stored as a database, and the more accurate one-sided elongation value of the step bending is obtained easily by less parameters including only two data including the plate thickness and the step bending angle based on the approximation formula. The bending is carried out efficiently and accurately based on the one-sided elongation value without previously carrying out trial step bending.